Transactions are automatically suspended when you have a transaction open and then switch to some other area to do something else.
Suspended transactions will remain suspended if a user looses his connection and then the transaction remains suspended even though the software that created the suspension is no longer running.
All transactions suspended will automatically become unsuspended when the last user logs out of the software.
Alternatively, you can unsuspend a transaction by selecting Toolbox|Unsuspend Transaction, from any transaction menu.
Do not unsuspend a transaction that is legitimately suspended, as this will cause a user on the network to loose their work.
Try to unsuspend the transaction on the computer where the suspension originally occurred. This may allow the user to recover any data that was entered on it, as the system does background back-ups as you type.
If the backup is not recovered, or there is nothing to recover, unsuspending a transaction at least allows you to recover the reserved transaction number.